A graphene is a two-dimensional crystal composed of carbon atoms. The graphene is a material that has attracted great attention since it was discovered in 2004. The graphene has excellent electrical, thermal, optical and mechanical properties, and is expected to be applied in a wide range of fields such as those of battery materials, energy storage materials, electronic devices and composite materials.
Examples of a method for producing a graphene include mechanical separation methods, CVD (chemical vapor deposition) methods and CEG (crystal epitaxial growth) methods. Among them, an oxidation-reduction method, i.e., a method in which graphite oxide is obtained by oxidizing natural graphite, and then subjected to a reduction reaction to produce a graphene is promising as an industrial production method because the method is capable of mass-producing the graphene.
For enlarging the application range of the graphene, it is useful to use the graphene in the form of a dispersion so that the graphene is kneaded with a resin, or mixed with an electrode paste for batteries. However, the graphene aggregates easily, and it is thus difficult to prepare a graphene dispersion with high-concentration.
Studies have been conducted on use of various kinds of dispersants for improving the dispersibility of the graphene. Patent Document 1 discloses a technique for dispersing a graphene using a surfactant as a dispersant. Patent Document 2 discloses improvement of dispersibility using a polycyclic aromatic compound.